The invention relates to a belt retractor for a vehicle seat belt.
Belt retractors comprise a vehicle-sensitive locking system usually provided with a sensor which normally includes, as an inertia mass, a metal ball which is movably supported in a shell fixed to the housing. A sensor lever which is pivoted to a housing and is swiveled about its pivot bearing by the movement of the metal ball rests on the metal ball. During said swivel of the sensor lever, the end thereof enters the path of motion of control teeth at the periphery of a control disk arranged on the belt reel so as to be rotatable to a limited extent. In this way the control disk is locked so that a relative rotation occurs between the control disk and the belt reel. Said relative rotation is exploited to move a locking blade pivoted to a frame of the belt retractor into locking engagement with locking teeth being associated with the belt reel.
When running on an uneven road, vibrations of the vehicle body will occur which cause the metal ball and, consequently, also the sensor lever to be deflected at short intervals, thus producing disturbing noise.
For reducing said disturbing noise use is made of belt retractors including an idler arm which is coupled to the belt reel via a friction coupling and prevents the metal ball from deflecting. Such belt retractor is known, for example, from DE 10 2006 037 544 A1.
However, it is not always possible to design the known belt retractors in an optimum manner, however, due to the partially contrary requirements as regards the maximum admissible locking path and a significant noise reduction in the real vehicle environment and during normal driving.